installable file system

(IFS or "File System Driver", "FSD") An
API that allows you to extend OS/2 to access files stored
on disk in formats other than FAT and HPFS, and access
files that are stored on a network file server.

For example an IFS could provide programs running under OS/2
(including DOS and Windows programs) with access to files
stored under Unix using the Berkeley fast file system.

The other variety of IFS (a "remote file system" or
"redirector") allows file sharing over a LAN, e.g. using
Unix's Network File Systemprotocol. In this case, the
IFS passes a program's file access requests to a remote file
server, possibly also translating between different file
attributes used by OS/2 and the remote system.

Documentation on the IFS API has been available only by
special request from IBM.

An IFS is structured as an ordinary 16-bit DLL with entry
points for opening, closing, reading, and writing files, the
swapper, file locking, and Universal Naming Convention. The
main part of an IFS that runs in ring 0 is called by the
OS/2 kernel in the context of the caller's process and
thread. The other part that runs in ring 3 is a utility
library with entry points for FORMAT, RECOVER, SYS, and
CHKDSK.

The installer commonly asks the user to enter desired
configuration options for the main program or hardware, and
sets up various initialisation files accordingly, as well as
copying the main program to a hard disc.

Some badly designed operating systems require applications to
provide an uninstaller because of the number of different
files modified or created during the installation process.